DESCRIPTION: (Applicant's Abstract) Evidence from the scientific literature indicates that uncorrected astigmatism during childhood is associated with three types of amblyopia: (1) a difference in best-corrected acuity and contrast sensitivity for orthogonal gratings (meridional amblyopia or MA), (2) a difference in best-corrected acuity for orthogonally-oriented vernier acuity stimuli (also termed MA), and (3) a deficit in best-corrected recognition (letter) acuity. These data suggest the presence of a sensitive period for the development of astigmatism-related amblyopia. However, only limited information is available concerning factors that influence the development and treatment of astigmatism-related amblyopia. The lack of research regarding astigmatism-related amblyopia is most likely due to the low prevalence of astigmatism in most populations of children. However, a high prevalence of large amounts of astigmatism and astigmatism-related amblyopia has been documented in members of the Tohono O'Odham grade-school children are not currently wearing eyeglass correction. The presence of this large sample of uncorrected highly astigmatic children provides a unique opportunity for the study of the development and treatment of astigmatism-related amblyopia. The goals of the present study are: (1) to characterize vision deficits associated with astigmatism-related amblyopia (through measurements of grating acuity, vernier acuity, recognition acuity, and contrast sensitivity), (2) to identify factors influencing the development of astigmatism-related amblyopia (e.g., factors such as amount and type of astigmatism), and (3) to determine age-specific effects of glasses intervention on astigmatism-related amblyopia. The proposed study will provide valuable clinical information regarding the development and treatment of astigmatism-related amblyopia. In addition, it will provide a valuable public health service to members of the Tohono O'Odham.